Mating in sharks has been rarely observed, but most species do it while they swim parallel to each other and the male inserts a clasper into female's oviduct.
There are three ways in which shark pups are born:
Oviparity. Sharks lay eggs.
Viviparity Sharks have placental links with developing pups. Pups born fully functional.
Ovoviviparity Method used by most shark species. Eggs develop inside the oviduct and hatch inside the oviduct where it finishes its development. Pups born fully functional.